LCD / OLED Display
Optoelectronic
A display technology that uses liquid crystals (LCD) or organic light-emitting diodes (OLED) to present visual information. Common in smartphones, monitors, and embedded systems.
What it looks like
LCD / OLED Display
A typical optoelectronic — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
Resolution
pixels (width x height)Number of pixels on the display (e.g., 128x64, 1920x1080). Higher = more detail.
Interface
ProtocolCommunication method: I2C, SPI, parallel, HDMI, MIPI DSI.
Color depth
bitsNumber of colors each pixel can display (e.g., 8-bit = 256 colors per channel).
Viewing angle
degreesMaximum angle where display remains visible (e.g., 178° for IPS panels).
Backlight
cd/m² (nits)Brightness for LCDs (OLEDs are self-emitting). Higher = better visibility in light.
Laws that govern it
- Ohm's lawV = I × R
The backlight is an LED string and needs a current-limiting resistor — the omission that quietly kills 1602 modules.
- Kirchhoff's voltage law (KVL)ΣV(loop) = 0
The contrast pin wants a voltage from a divider or trimmer; get that loop wrong and you see either a blank screen or black boxes.
- Law of capacitance — capacitance formula Q = CVQ = C × V, i = C·dv/dt, E = ½CV²
OLED modules pulse their charge pump, so without local bulk capacitance the display flickers and the I²C bus starts erroring.
Each law is stated in full — with its diagram, variables and worked meaning — on the electrical laws page.
Markings
Usually has model number printed on the back (e.g., '1602A' for 16x2 LCD). Interface pins labeled on PCB edge.
Standard values
Common resolutions: 128x64, 128x32, 240x240, 320x240. Common sizes: 0.96", 1.3", 1.8", 2.4", 3.5".
How to choose
1) Determine required resolution and size for your application. 2) Check interface compatibility with your microcontroller (I2C vs SPI). 3) Consider color needs (monochrome vs color). 4) Evaluate viewing angle and brightness requirements. 5) Check operating voltage (3.3V vs 5V).
Pinout & package
Typically 8-40 pins. Common pins: VCC, GND, V0 (contrast), RS (register select), RW (read/write), E (enable), D0-D7 (data), A/K (backlight anode/cathode). Packages: module with PCB board, bare glass panel.
Example circuits
- Arduino with 16x2 LCD via I2C backpack
- Raspberry Pi touchscreen interface
- OLED display on ESP32 for IoT status
- Automotive dashboard cluster display
Common failures
Dead pixels (stuck on/off), backlight failure (no light), damaged connector pins, liquid crystal leakage (dark spots), screen flickering, controller IC failure.
How to test
1) Apply correct voltage and backlight. 2) Send test pattern via microcontroller. 3) Check for uniform backlight and no dead pixels. 4) Verify all segments respond correctly. For OLED, check for color uniformity.
Substitutes
Different size/resolution with same interface. Can use LCD to OLED adapters (with driver changes). Touchscreen versions add touch functionality.